BERLIN — Ulrich Renz, the former head of the Associated Press’ German-language service who also covered the trials of Auschwitz death camp leaders in World War II, has died at the age of 90.

Renz died on Monday, according to Peter Gehrig, his close friend of 50 years and a former AP colleague who lived in the same old people’s home in Frankfurt. No cause of death was stated.

Renz, commonly known as “Uli,” began working for the AP in Germany in 1971, following a stint at United Press International. At AP, he first worked on the foreign desk and eventually headed the German language service at headquarters in Frankfurt from 1986-92.

The German-language news service was launched after World War II to help establish a free press and promote democracy in post-war West Germany. It was sold to German news agency DDP in 2009.

Renz was born in Stuttgart in 1934 and grew up in the village of Giengen an der Brenz in southwestern Germany. After graduating from high school, he worked as a reporter for the Heidenheimer Zeitung newspaper, where he remained until moving to UPI in 1959.

During his decades as a journalist in Germany, he focused on reporting on the Federal Constitutional Court, the country’s highest court, and wrote extensively about the trials of many former Nazis, including the Auschwitz trials.

The trial in Frankfurt in 1963-65 of 22 people who helped run the Auschwitz death camp in German-occupied Poland, the Allied War II. It was one of the biggest trials since the Nuremberg war crimes trials in the immediate aftermath of World War II. It confronted people in then-West Germany with its Nazi past and is considered a turning point in Germany’s efforts to address crimes at the time.

After retiring in 1992, Renz devoted his time to researching the life of carpenter Georg Elser, who tried to kill Hitler in Munich but was thwarted when the Nazi leader unexpectedly left the room minutes before the bomb exploded. Renz published several books about Elser’s life and his failed venture, gaining recognition from scholars and political leaders. He was honored with the German Cross of Honor for his work.

“Renz’s passion for researching the Third Reich stemmed at least in part from his father’s refusal, as a civilian administrator in Nazi-occupied Poland, to talk about his role in it,” Gehrig said. “In defeated Germany, there was little interest in investigating the dark past. Uli was among the young Germans who thought otherwise.”

Former AP Bonn correspondent Terrence Petty said that “as a journalist and an investigator of disturbing truths, Uli was an inspiration to those who knew and worked with him, including me.”

Gehrig said Renz loved cycling, visiting cafes in Frankfurt and reading books, but his eyesight had been declining lately.

Renz is survived by his son, daughter-in-law and grandson.